1. Field of the Invention
The present invention relates to an automatic document feeder for use in image readers such as copying machines, facsimile machines, etc.
2. Description of the Related Art
Conventionally, automatic document feeders installed on a copying machine body are generally provided with such mechanism that documents placed on a feed tray are fed one by one automatically to a reading means installed in the copying machine body, and are then read by an optical system provided in the copying machine and discharged onto a discharging tray. In order to realize high-speed conveyance of documents, there have been proposed some arrangements in that, for example, documents are conveyed at a high-speed after they are read, and then discharged onto a discharging tray (Japanese Laid-open Utility Model No. 55157 of 1993), or documents are conveyed at high speed after they are read, and then slowed down just before discharging so as to be discharged gently onto a discharging tray (Japanese Laid-open Patent No. 178363 of 1986).
If documents are conveyed at high speed and discharged after they are read in such a conventional automatic document feeder, however, the documents often fly out onto the discharging tray so as to be scattered. This arises a problem of poor alignment of the documents. In addition, if the document feeding is slowed down just before discharging, another problem arises wherein the high conveying speed is sacrificed, although the above-mentioned poor alignment problem is solved. In the cases described above, therefore, the following document cannot be conveyed before the preceding document is discharged since there is a difference between reading and discharging speeds of documents. Consequently, such conventional arrangements include possibilities whereby the total processing speed of the automatic document feeder may be lowered.
Under such the circumstances, the object of the present invention is to provide an automatic document feeder that can solve the problem of poor alignment of discharged documents on a discharging tray, as well as improve the total processing speed of the document feeder.